Sustainable Management of Salt Slag

Isabel Padilla, Maximina Romero, Sol López-Andrés and Aurora López-Delgado
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Isabel Padilla: “Eduardo Torroja” Institute for Construction Sciences, IETcc-CSIC, 28033 Madrid, Spain
Maximina Romero: “Eduardo Torroja” Institute for Construction Sciences, IETcc-CSIC, 28033 Madrid, Spain
Sol López-Andrés: Department of Mineralogy and Petrology, Faculty of Geology, University Complutense of Madrid, 28040 Madrid, Spain
Aurora López-Delgado: “Eduardo Torroja” Institute for Construction Sciences, IETcc-CSIC, 28033 Madrid, Spain

Sustainability, 2022, vol. 14, issue 9, 1-13

Abstract: The management of salt slag, a waste from the secondary aluminum industry, is associated with huge environmental concerns due to the risk of atmospheric pollution (emission of toxic gases), groundwater contamination (high salt content that can percolate and cause an increase in salinity) and soil unavailability (large extensions required for disposal). Therefore, the development of a sustainable process for its treatment and recovery is of the utmost importance. In this work, a two-step process for the valorization of salt slag was developed that rendered zeolite as the main added-value product and NaCl and NH 3 as byproducts. First, salt slag was hydrolyzed at 90 °C and at a solid/water ratio of 1/3. More than 90% of salt and ~90% of ammonia were recovered. In a second step, the hydrolyzed slag was completely transformed into a NaP zeolite under mild hydrothermal conditions. The zeolite exhibited specific surface area (17 m 2 g −1 ), cation exchange capacity (2.12 meq g −1 ) and zeta potential (−52 mV) values that represent good characteristics for use in the removal of metal ions from aqueous effluents. The transformation of salt slag into zeolite can be considered a sustainable process with a high contribution to the circular economy.

Keywords: zeolite; salt slag; hazardous waste; hydrolysis; hydrothermal synthesis; sustainability; waste management; aluminum waste (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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